§1.1 Field of the Invention
The present invention concerns determining a location or position. In particular, the present invention concerns avoiding problems of various individual location and positioning technologies to generate an improved location or position, as well as uses of such an improved location or position.
§1.2 Background Information
Over the last few decades, interest in locating and tracking objects has exploded. Radar and related technologies have been around for a long time. With radar, an object is tracked using electromagnetic radiation reflected by an uncooperative object. A number of location technologies have been developed including global positioning satellite (GPS), triangulation, “radio camera,” angle of arrival, time of arrival, time difference of arrival and phase difference of arrival, and power signature. Each of the foregoing location technologies are designed to work under certain assumptions and satisfy a certain set of needs of the end user. Unfortunately, each of the individual location technologies has shortcomings, some of which are introduced below.
For example, radio frequency based location technologies use various licensed and unlicensed frequency bands, may require the existence of a line-of-sight path between receivers and the tracked object(s), may require the availability of battery powered (active) tags or passive tags, and may be accurate anywhere from a few inches to tens of meters. As another example, at least some of these technologies may require non-interference from other spectrum users, a willingness to manually calibrate the entire positioning area and system, and an affordability to pay for the tags whose costs range from a few cents to a few hundred dollars.
As another example, Wi-Fi, 3G and various location technologies employing sonar, radar, proximity devices that use capacity, inductance, etc., assume the presence of various wireless networking infrastructure,
Some technologies such as GPS work well outdoors, but not so well indoors (because multi-path may occur due to reflections and diffractions in an indoor environment). Conversely, other technologies, such as Wi-Fi-based (IEEE 802.11) location technologies work well indoors, but not so well outdoors (because they require that a network of receivers be placed wherever the objects of interest may reside).
Line-of-sight location technologies can be affected by environment (e.g., air, rubble, metal, buildings, etc.) between receivers and an object of interest, and may require a priori knowledge of such environment. Therefore time-of-arrival based systems need to find a way to account for non-line-of-sight paths as they interfere with accurate time estimates, thereby impacting the accuracy.
In view of the foregoing limits of current individual location technologies, it would be useful to provide methods and apparatus for generating improved (e.g., more accurate, less expensive, more versatile) location determination, particularly one that works in both indoor and outdoor environments.